Fix edge cases writing certain length coded values

Author: dougwilson

Changes.md

@@ -10,6 +10,7 @@ you spot any mistakes.
 * Add `query` method to `PoolNamespace` #1256 #1505 #1506
   - Used as `cluster.of(...).query(...)`
 * Add new error codes up to MySQL 5.7.16
+* Fix edge cases writing certain length coded values
 * Fix typo in `HANDSHAKE_NO_SSL_SUPPORT` error message #1534
 * Support Node.js 7.x
 * Update `bignumber.js` to 2.4.0

lib/protocol/PacketWriter.js

@@ -116,10 +116,10 @@ PacketWriter.prototype.writeLengthCodedNumber = function(value) {
     );
   }
 
-  if (value <= BIT_16) {
+  if (value < BIT_16) {
     this._allocate(3);
     this._buffer[this._offset++] = 252;
-  } else if (value <= BIT_24) {
+  } else if (value < BIT_24) {
     this._allocate(4);
     this._buffer[this._offset++] = 253;
   } else {
@@ -131,12 +131,16 @@ PacketWriter.prototype.writeLengthCodedNumber = function(value) {
   this._buffer[this._offset++] = value & 0xff;
   this._buffer[this._offset++] = (value >> 8) & 0xff;
 
-  if (value <= BIT_16) return;
+  if (value < BIT_16) {
+    return;
+  }
 
   // 24 Bit
   this._buffer[this._offset++] = (value >> 16) & 0xff;
 
-  if (value <= BIT_24) return;
+  if (value < BIT_24) {
+    return;
+  }
 
   this._buffer[this._offset++] = (value >> 24) & 0xff;
 

test/unit/connection/test-large-blobs.js

@@ -0,0 +1,85 @@
+var assert     = require('assert');
+var common     = require('../../common');
+var connection = common.createConnection({port: common.fakeServerPort});
+var server     = common.createFakeServer();
+
+server.listen(common.fakeServerPort, function (err) {
+  assert.ifError(err);
+
+  connection.query('SELECT value FROM blobs', function (err, rows) {
+    assert.ifError(err);
+    assert.equal(rows.length, 6);
+    assert.equal(rows[0].value.length, 0);
+    assert.equal(rows[1].value.length, 8);
+    assert.equal(rows[2].value.length, (Math.pow(2, 16) - 1));
+    assert.equal(rows[3].value.length, Math.pow(2, 16));
+    assert.equal(rows[4].value.length, (Math.pow(2, 24) - 1));
+    assert.equal(rows[5].value.length, Math.pow(2, 24));
+
+    connection.destroy();
+    server.destroy();
+  });
+});
+
+server.on('connection', function(conn) {
+  conn.handshake();
+  conn.on('query', function(packet) {
+    switch (packet.sql) {
+      case 'SELECT value FROM blobs':
+        this._sendPacket(new common.Packets.ResultSetHeaderPacket({
+          fieldCount: 1
+        }));
+
+        this._sendPacket(new common.Packets.FieldPacket({
+          catalog    : 'def',
+          charsetNr  : common.Charsets.BINARY,
+          name       : 'value',
+          protocol41 : true,
+          type       : common.Types.LONG_BLOB
+        }));
+
+        this._sendPacket(new common.Packets.EofPacket());
+
+        var writer = new common.PacketWriter();
+        writer.writeLengthCodedBuffer(new Buffer(0));
+        this._socket.write(writer.toBuffer(this._parser));
+
+        var writer = new common.PacketWriter();
+        writer.writeLengthCodedBuffer(filledBuffer(8, '.'));
+        this._socket.write(writer.toBuffer(this._parser));
+
+        var writer = new common.PacketWriter();
+        writer.writeLengthCodedBuffer(filledBuffer((Math.pow(2, 16) - 1), '.'));
+        this._socket.write(writer.toBuffer(this._parser));
+
+        var writer = new common.PacketWriter();
+        writer.writeLengthCodedBuffer(filledBuffer(Math.pow(2, 16), '.'));
+        this._socket.write(writer.toBuffer(this._parser));
+
+        var writer = new common.PacketWriter();
+        writer.writeLengthCodedBuffer(filledBuffer((Math.pow(2, 24) - 1), '.'));
+        this._socket.write(writer.toBuffer(this._parser));
+
+        var writer = new common.PacketWriter();
+        writer.writeLengthCodedBuffer(filledBuffer(Math.pow(2, 24), '.'));
+        this._socket.write(writer.toBuffer(this._parser));
+
+        this._sendPacket(new common.Packets.EofPacket());
+        this._parser.resetPacketNumber();
+        break;
+      default:
+        this._handlePacketQuery(packet);
+        break;
+    }
+  });
+});
+
+function filledBuffer(size, fill) {
+  if (Buffer.alloc) {
+    return Buffer.alloc(size, fill);
+  }
+
+  var buf = new Buffer(size);
+  buf.fill(fill);
+  return buf;
+}